Characteristics of MBE-grown GaN detectors on double buffer layers under high-power ultraviolet optical irradiation

In this paper, we present experimental investigations on the radiation hardness of GaN-based Schottky diode photodetectors. High-power ultraviolet (UV) radiation obtained from a Xenon lamp is used as the light source for the optical-stressing experiment. Two types of devices are being investigated. One has a double-buffer-layer structure that consists of a conventional high-temperature AIN buffer layer and an intermediate temperature buffer layer (type 1), and the control device was fabricated with only a conventional AIN buffer layer (type 11). Detailed current-voltage, capacitance-voltage, flicker noise, and responsivity measurements performed on the detectors show that the degradations of the devices arose from the defects present at the Schottky junctions due to the exposure of the devices to the high-power UV radiation. Both types of devices exhibit degradation in their optoelectronic properties. However, type-I devices, in general, exhibit gradual and slow degradation, whereas type-II devices exhibit catastrophic breakdowns in the device characteristics. Our experimental data indicate significant improvement in the radiation hardness for type-I devices.